Journal Article

102 The effect of a central arterial venous anastomosis on cardiac haemodynamics and right atrial and ventricular volumes during orthostasis

Van Zalen, Jet, Freemantle, Nicholas, Marshall, Andrew, Furniss, Stephen, Dulai, Rajdip, Sulke, Neil

2020

Overview

IntroductionOrthostasis induces a rapid and large gravity-related shift of 500-1000mls of blood volume from the thorax to below the diaphragm. It has been reported that the central mechanism in patients with orthostatic intolerance is due to this gravity shift and related hypotension.The ROX Coupler is a device that allows creation of a central arteriovenous anastomosis at the iliac level resulting in an A-V shunt of 0.8L/m. We performed a prospective controlled study investigating the effects of the ROX Coupler on cardiac haemodynamics and right heart parameters during orthostasis compared to age matched controls.Methods10 patients with a ROX Coupler were compared to 10 age matched controls during an active stand at baseline, 30, 60, 90 and 120 seconds. Cardiac haemodynamics were measured using impedance cardiography and non-invasive beat-to-beat monitoring (Task Force® Monitor) along with right-sided echocardiography. An independent-group t-test was used to compare baseline variables and demographics. Differences in cardiac haemodynamics and right-sided echocardiography were compared within each group at the specific time intervals using repeated measures analysis of variance. Significance was established at P <0.05.ResultsThere was no significant difference in age (68.40 ± 7.09 vs 69.40 ± 11.09, p = 0.81) or BMI (29.1± 4.52 vs 27.72 ± 4.8, p = 0.51) between ROX Coupler patients and controls. At baseline ROX Coupler patients had a significantly higher cardiac index and lower indexed total peripheral resistance (Table 1). ROX Coupler patients also had a significantly higher right ventricular end systolic volume (RV ESV), right ventricular end diastolic volume (RVEDV) and right atrial end diastolic volume (RAEDV) than controls (Table 2).Abstract 102 Table 1Baseline comparison of cardiac haemodynamicsRox CouplerControlP Value Heart rate80.0 ± 12.574.2 ± 12.40.31Systolic BP129.1 ± 21.2127.8 ± 17.10.88Diastolic BP74.8 ± 18.681.6 ± 14.10.37Stroke Index38.6 ± 11.334.6 ± 5.00.32Cardiac Index3.2 ± 0.82.5 ± 0.50.03Total peripheral resistance2729 ± 10253855 ± 9990.02Thoracic fluid content27.6 ± 4.130.1 ± 5.30.24Abbreviations: BP Blood pressure. Values given as mean ± Standard deviationAbstract 102 Table 2Baseline comparison of right sided parametersRox CouplerControlP value RV ESV (ml)15.3 ± 2.99.7 ± 4.70.05RV EDV (ml)39.0 ± 6.928.0 ± 8.50.05RV (EF%)58.6 ± 5.865.7 ± 9.00.15RV SV (ml)22.3 ± 5.518.7 ± 5.90.37RA ESV (ml)34.7 ± 12.644.8 ± 16.50.17RA EDV (ml)55.7 ± 2028.5 ± 9.70.003Abbreviations: ESV end systolic volume; EDV end diastolic volume; EF ejection fraction; SV stroke volume. Values given as mean ± Standard deviationDuring active stand there was a significant decrease in systolic blood pressure from baseline in controls (p=0.04) however in ROX Coupler patients systolic blood pressure was non-significantly different from baseline (p = 0.59) as shown in figure 1. There was no significant difference in indexed total peripheral resistance from baseline in either group. Cardiac index and total thoracic content significantly reduced from baseline in both groups.Abstract 102 Figure 1Change in systolic blood pressure during active standThere was no significant difference in RV ESV, RV EDV, RV ejection fraction, RA EDV or RA ESV during active stand.ConclusionsThe Rox Coupler resulted in a reduction in immediate orthostatic hypotension compared to age matched controls. Cardiac index was higher in ROX Coupler patients, which is expected given the higher pre load effects of the anastomosis. The higher cardiac output and right-sided volumes may explain the maintenance in systolic blood pressure during orthostasis and warrants further investigation.Conflict of InterestNone

• Publisher: BMJ Publishing Group LTD
• Subject: Age / Blood pressure / Ejection fraction / Hemodynamics / Hypotension